Physio: Renal Processing H+/HCO3- Flashcards
Among the most important problems confronting clinicians in the hospital setting?
Acid-Base imbalance
Organs involved in excretion of acids and bases and maintenance of acid-base balance
- Kidneys
- Lungs
Plasma H+ is constantly altered by…
- Metabolism of ingested food
- Secretions from GI tract
- De novo generation of acids and bases from fat and glycogen metabolism
- Changes in production of CO2
Normal H is around 40nM (pH=7.4)
Normal range of arterial pH
7.37-7.42
What are the 3 mechanisms that contribute to maintaining pH in the normal range?
- Buffering of ECF and ICF (sec-min)
- Respiratory compensation (min-hr)
- Renal compensation (hrs-days)
Buffer systems involve a set of 3 interacting substances….
- Acid
- Conjugate base
- H+ (proton)
Acid conjugate base + [H+]
R-COOH [R-COO-] + [H+]
It does NOT eliminate acids/bases
It limits the effects on acid/bases on blood pH
What are ECF buffer systems?
Phosphate and albumin
What are ICF buffer systems?
Hb in RBC
What are 3 types of acids?
Fixed Acids
Titratable acid
Volatile acid
Fixed acid
Non-volatile acids, metabolic acids
H2SO4 (catabolism of AA)
H3PO4 (phospholipids)
B-hydroxybutyric acid and acetoacetic acid (keto acids) Lactic Acid (exercise)
Salicylate acid, formic acid, glycolid and oxalis acid (acid overdose, MetOF and ethylene glycol ingestion)
Titratable acid
Acid that can lose H+ in an acid/base rxn
Ex: H2PO4- (NOT NH4+ !!!!!)
Volatile acids
Carbonic acid (H2CO3)
Product of CO2 and H20 (reversible rxn)
Most important buffer system
CO2/HCO3- buffer system
- CO2 and HCO3- are regulated independently
- CO2 acts like a weak acid
- It combines with H20 to form carbonic acid
- Reaction to form carbonic acid is slow
- most tissues express carbonic anhydride to accelerate the Rxn
Fixed acids must be buffered….
In the bloody fluids and excreted by the kidneys
What are the plasma levels of most solutes?
2-130mM
Normal H+ = 40nM
